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R65 High Idle After Backfire

A few days ago, my '83 R65 backfired twice through the right carb while I was trying to start it. I added more choke and it fired and ran nicely... except: Now, after about 20-30 minutes of riding, when the engine is hot, it doesn't want to settle down to a regular idle. If I am slowing or stopping, the bike will hold its RPM when the clutch is in, even if the throttle is closed. If I downshift and let the brakes bring the engine below 2,000 RPM, I can pull in the clutch and the engine will settle down to its normal (800-900RPM) idle. Upshifting is fun, because when I accelerate and pull in the clutch for an upshift, the engine stays at the RPM it was at in the lower gear until I let the clutch out.

The Bing carbs were re-built about 400 miles ago by Re-Psycle in Lithopolis, Ohio and up until the backfire there were no problems.

Could the backfiring have stretched a diaphragm or messed anything else up? Any and all ideas and suggestions will be greatly appreciated

I would suspect your backfire cause an air leak someplace in the right carburetor or intake. The first place I would look is at the enricher as the gasket may have been damaged. I would also check to make sure there is no leaks around the coupling between the carburetor and head. Spray that area with WD40 when running and see if the idle changes. You can do the same around the enricher to check for an air leak.

I would not suspect a diaphragm problem unless you had an issue with acceleration.

Thanks for the info!

Thanks Gents,
I've checked the carb connections, etc and they look good. I found a how-to for removing, disassembling, cleaning, checking, and rebuilding the ignition canister. I hope to get a look at that over the Labor Day weekend. The idea of a sticky mechanical advance sounds good, especially since slowing the engine by braking gets the idle to drop.
Thanks again for the input.